UnderKi
by Joker the prince of all crime
Summary: AU. In this world everyone has access to the power of Ki, the spiritual energy of the universe. But very few have access to the power of Determination, the power to control the timeline. The three that can, Sans, Chara, and Frisk, are all going to war because of their plans. Chara's to kill all humans, Sans' to protect his brother, Frisk's to free everyone.
**Disclaimer: I don't own Undertale or any of it's affiliates. However I do own my own OCs and the plot of this story.**

"Ahahahaha! Oh isn't this absolutely _wonderful_ Frisky?" The brown-haired, red eyed female said to the strangely twin-like male.

'If your idea of wonderful is nearly getting your head taken off, Chara, then I guess it is!" Frisk called over from the other end of the Judgement Hall.

"I'M GONNA TO KILL YOU BOTH!" The deep-ish voice of Sans yelled from a pile of rubble, which, shortly after his yell, exploded violently, revealing Sans himself. His eye glowed blue and he looked on the verge of unleashing all his power. "You for killing Papyrus!" He said pointing to Chara, who feigned innocence.

"Who? Me? It was Frisky over there who _let_ me do it. _Sansy"_ She said, adding extra venom in her voice as she gave his nickname to him _._

 _"_ And you for letting her!" Sans yelled pointing at Frisk, who looked resigned.

"Sans, I had to try something, it was my only other way to free everyone, maybe a true pacifist isn't what we need, nor a true genocide, but rather we need a neutral route. Some die, some live." Frisk tried to explain to his fellow enraged Ki user.

"OF ALL THE MONSTERS IN THE UNDERGROUND YOU LET HER KILL HIM THOUGH?!" Came Sans' reply.

"Enough talk. You said you were going to kill us both, so lets see what you've got." Chara said cutting in with a grin on her face.

She then raised her hand up and charged a ball of red Ki in her hands, putting an insane grin on her face. She aimed at Frisk, but tossed it lazily to the side at Sans. He narrowly dodged, and made a finger pistol and fired a Gaster Blaster at her, and he did the same with the other hand, aiming at Frisk.

Frisk looked at Chara and she looked back, then they both leaped up and dodged the Ki attacks. Chara, having enough of fighting with energy, and flew after Sans with her knife flashing from inside her sleeve. She and Sans clashed mid-air and traded blow after blow, neither being able to hit the other.

Frisk sighed. "I'm going to have to reset again aren't I? Good thing Chara didn't bother to SAVE this time around or else this would be difficult."

Ah yes in this world each of them have piece of the timeline under their control. Sans had the power to see into different timelines, different routes. Chara could SAVE and go back to those SAVES anytime she wanted. And Frisk? Well he got arguably the best power out of the three: the ability to Reset the world and go back to to the beginning of his journey, or go to any one of Chara's SAVES that she allowed him to. As going back to the beginning always made things so difficult, as it meant he'd have to meet all his friends over again.

He glanced back at the battle between the two virtually mortal enemies. Sans had transformed it had seemed, and Chara looked like she was coming close to transforming too. Sans' transformation made him look like a skeletal dragon without wings and also caused him to grow to be several feet tall. His right eye still glowed blue in this form and his theme still played in the background, barely audible to them unless they paid real attention to it. _"I sure am glad I made Chara SAVE back at mom's house after I knocked some sense into King Asgore."_ Frisk thought as he began to power up, a bright white aura rapping around him defensively. He flew between the two, who were charging up to all-powerful blasts, Sans's coming from his dragon-like maw, Chara's appearing from an outstretched finger.

"Execution Beam!" Chara sing-songed as she fired it.

"Hope Ray!" Sans' deep voice called as he threw his head forward and fired the beam.

Frisk put his hands out lazily, and called. "I don't know why you two insist on naming your blasts, it seems stupid to me but..." Frisk put on an uncharacteristic smirk. "Mercy Blast!" He called firing twin light blue blasts that slammed into the others own blasts, keeping them at bay for now.

"Okay Frisky, guess its time to pull out my own transformation!" Chara said as her blast was slowly being pushed back by Frisk's. She then grinned madly and pulled her hands away from their jobs, then she threw them out to to the sides and began to power up with a yell, one that morphed into a laugh.

"AAAAAAHHHHHAHAHAHAHAHAHAHA! AHAHAHAHAHAHAHA!" Her laugh got higher and higher pitched as a force field formed around her, and the transformation took hold. Her nails got longer and turned a deep blood red, the red of her eyes consumed her entire eye sockets and her teeth sharpened to deadly, sharp, points, finally two black wings sprouted from her back and she grew two more feet. Strangely her pretty features seemed only to enhance while in this state, causing her to look much prettier than usual.

She cracked her neck on both sides and gave a sigh of content. "Oh, yes. It's been _too_ long since I've used this form, _too_ long since I stretched my wings and felt someone's blood hit my nails rather than my knife. She looked down at Frisk and over at Sans with a deathly smile gracing her lips. "So _Frisky, Sansy_ how do you two feel knowing that i'm going to kill you both, preferably you first Sans so Frisky can't reset until after i'm done with you."She asked landing on the ground in front of them.

"Well kid, can't say i'm too surprised you'd say that but i don't think i'm going to let it happen. I got a real _Bone_ to pick with you, both of you."He added looking at Frisk with contempt. "But I kinda don't wanna have'ta fight you in that form until i'm fully healed so..." He trailed off and shoved Frisk in front of him. "Reset Frisk!" He yelled firing a Ki blast into Frisk's back, vaporizing him.

"Grr, _Sansy, dear"_ Chara hissed at the skeleton with contempt, turning to him.

"Hehe sorry kid... Wait, no i'm not. I never really liked your CHARActor to begin with." He said with a shrug.

"Oh when Frisk resets your DEAD Sans." She called before giving a smirk. "I guess it really BROTHERS you that i'm still alive here though, huh?"

"..Shut up." Came his reply after a few seconds. Then the whole world started to change, as per the usual with resets, and they felt themselves being pulled back to where they were when Chara had first saved...

Chara's eyes fluttered open dreamily, next to her laid Frisk, whose eyes opened slowly too. Sans was watching them from afar, standing behind the tree he always stood behind. "Mm, Frisky." Chara purred, stretching. "Your dead." She said now fully awake, and towering over him, red Ki blast in hand. Sans theme began to play in their ears as Chara was lifted into the air.

"Hey kid, you always did have an UPLIFTING personality." He said raising her higher.

"Sans, I was only _joking."_ Chara said, adding extra emphasis on 'joking'. "NOW PUT ME DOWN!" She yelled shortly after.

'Sure kid, as long as nobody dies this time around." Sans said dropping her, and letting her float to the ground herself.

Chara grinned and pulled out her map of previous saves. "No promises!"She called and leapt into a save point somewhere in Hotlands.

"Well, I gotta go make sure she doesn't get in trouble." Sans said, and then immediately walked in the opposite direction from Hotlands.

Frisk stood up and dusted himself off, he could smell Toriel's butterscotch pie from the window her new home in Snowdin, as per Frisk's request (And to Chara's dismay). He quickly headed inside and found his adoptive Goat Mom...And her famous pie.

 **Author's note: I'm only going to give information about this AU in this author's note so here we go (this will be done in list form).**

 **1\. Chara and Frisk fell around the same time in this AU and are each 16.**

 **2\. Chara is a girl and Frisk is a guy, because it's my head-canon that she's female, as for Frisk...it's just plain easier to make him a guy in this AU.**

 **3\. Their will be hints of one-sided Charisk with Chara having slight Yandere-ish feelings for Frisk, but nothing too serious for those who don't like the ship.**

 **4\. When they fell Chara was put into a coma and Frisk thought her dead, and he went out to complete a pacifist route.**

 **5\. after waking up Chara convinced Frisk to reset and put him into a coma instead so she could complete a genocide route. After which she was stopped by Frisk, who had been woken up by Sans, who was searching for survivors at the time.**

 **7\. Together they stopped her from breaking the barrier and killing all humans, but at the cost of the other six souls being sent into each of them in turn and gave them each powers over the timeline as saw here.**

 **8\. Sans can not only see what happened last timeline, but he can see EVERYTHING that has happened before in his lifetime(s). Frisk can still reset but can only go to saves that Chara lets him go too, or he will have to reset all the way. Chara can travel to any save point she wants, but can only go into one other timeline than the main one, so she chooses to go to one that has no monsters anymore. Her timeline.**

 **9\. Ki is an energy that every monster has access to, some humans have it too but aren't very common.**

 **10\. Lastly transformations are few and far between, and only prodigies like Chara usually have them, but they can be unlocked through training.**

 **That is all the knowledge of this AU I have created so far, so i hope you enjoyed this and will review it. Also points for anyone who can figure out the anime I based this one ;).**

 **Until Next Time, True readers!**


End file.
